Dual firing rate oil burner apparatus



Oct. 19. 1948.

R. M. COCHRANE I DUAL FIRING RATE OIL BURNER APPARATUS Filed se i. 22, 1947 9 Sheets-Sheet 1 A. I I Q I INVENTOR 1P1 C/M RD N. Cac /mA/Yz ATTO NEYS v Oct. 19, 1948. R. M; COCHRANE 2,451,661

DUAL FIRING RATE OIL BURNER APPARATUS file/ mm 17. Coo/Mum ATTORN EYS Oct. 19, 1.948. R. M. COC HRANE v 2,451,661

DUAL FIRING RATE OIL BURNER APPARATUS Filed Sept. 22, 1947 9 Sheets-Sheet INVENTOR Oct. 19, 1948.

R. M. COCHRANE DUAL FIRING RATE OIL BURNER APPARATUS 9 Sheets- Sheet 4 Filed Sept. 22. 1947 INVENTOR RICHARD f1. Coca/941w ATTORN EYS Oct. 19,1948.

Filed Sept. 22, 1947 sm qa.

4 v R. M. COCHRANE 2,451,661

DUAL FIRING RATE OIL BURNER APPARATUS 7 Filed Sept. 22, 1947 9 Sheets-Sheet 6 'INVENT OR lP/cmvw 1% 6001/04:

ATTOR EYS Oct. 19, 1948. R. -M. COCHRANE W DUAL FIRING RATE OIL BURNER APPARATUS 9 Sheets-Sheet 7 Filed Sept.' 22, 1947 INVENTOR fl/cmmn 17. Car/m4:

I BY

ATTOR EYS Oct. 19, 1948. R. M. cocHRAN 2,451,661

DUAL FIRING RATE OIL BURNER APPARATUS 9 Sheets-Sheet 8 INVENTOR Rw /1017M. Che/M411:-

ATTOR EYS Oct. 19, 1948. R. M. COCHRANE DUAL FIRING RATE OIL BURNER APPARATUS 9 Sheets-Sheet 9 Filed Sept. 22, 1947 m3 wQQ U M INVENTOR RICHARD/7. [be/m4:

W Y W ATTOR EYS Patented Oct. 19, 1948 DUAL FIRING RATE OIL BURNER APPARATUS Richard M. Cochrane, West Springfield, Mass., assignor to Gilbert & Barker Manufacturing Company, Springfield, Mass., a corporation of Massachusetts I Application September 22, 1947, Serial No. 775,548

10 Claims. 1

This invention relates to improvements in oil burners which are adapted for house heating service and for intermittent operation at one or the other of two firing rates as may be selected manually or automatically by any suitable controlling means, to change the heating rate as changes in the weather occur.

In a burner of this type, having two oil-atomizing nozzles operable one at a time, one of the.

nozzles may be selected for operation and operate intermittently on and off over long periods, while the other of the nozzles remains idle. The idle nozzle contains oil which, if heated frequently, might in time'carbonize and cause stop-.

page of the nozzle.

This invention has for one object to provide improved automatic means for frequently operating for brief periods that nozzle which is not selected for operation for the purpose of purging such nozzle of oil before it becomes carbonized. This arrangement tends to keep the idle nozzle in good condition and to avoid stoppage due to carbonization.

The invention in this respect is an improvement on that disclosed in the application of Joseph A. Logan, filed December 10, 1946, under Serial No. 715,163, and assigned to the same assignee as the present application.

The invention has for another object the provision of improved automatic means, operable in the event that either one of the nozzles, which is selected for operation, becomes inoperable because of clogging or for any other reason, to connect the other nozzle for operation in its place.

The invention in this .respect is an improvement on that disclosed in the application of Joseph A. Logan, filed July 11, 1947, under Serial No. 760,396 and assigned to the samev assignee as the present application.

These and other objects and advantages will best be understood in connection with the description of one illustrative example of the invention shown in the accompanying drawings, in which: V

Fig. 1 is a side elevational view of an oil burner embodying the invention;

Fig. 2 is a sectional elevational view thereof;

Fig. 3 is an end elevational view with parts broken away and'parts in section, showing particularly the motor, fan and pump and'the control for the air inlet of the fan;

Fig. 4 is an enlarged fragmentary view of a detail connected with the air adjusting means;

Fig. 5 is a sectional plan view taken on the line 5-5 of Fi 1;

. 2 r Fig. 61s a sectional view showing the mounting of one of the oil atomizing nozzles;

Fig. 7 is a fragmentary sectional elevational view taken on the line 1-1 of Fig. 5;

Fig. 8 is a fragmentary cross sectional view taken on the line 88 of Fig. 3;

Fig. 9 is a fragmentary cross sectional view taken on the line 9-9 of Fig. 1;-

Fig. 10 is a sectional view taken on the line iii-l0 of Fig. 9;

Fig. 11 is a diagrammatical view of the connections between the pump, oil atomizing nozzles, air-shutter-operating motor and control valves;

Fig. 12 is a fragmentary view showing a modification in the diagram of Fig. 11;

Fig. 13 is a diagram showing one electri-calcontrol system for the burner including means for the selection of the high or low firing rate oil atomizing nozzle and a means for actuating the unselected nozzle briefly once during each cycle of operation of the burner; and

Fig. 14 is a diagram showing a modification of the electrical control system;

Figs. 15 and 16 are diagrams showing difi'erent positions of two contact fingers shown ,in Fig.

7 14; and

Fig. 17 is a diagram showing a further modification of the electrical control system.

In these drawings, there is shown a burner of the so-called gun type, wherein air is supplied by a fan through a conduit to mix with a spray of atomized oil produced by a nozzle, located in such conduit, usually near the outlet end thereof. In Fig. 2, the air supply fan is shown at I, mounted in a fan housing 4, which is formed in the upper part'of a casting 5, suitably supported from the floor, as by a pedestal 6. The air conduit is designated at- I. It is formed in part by an opening in the lower part of the casting 5 and in part by a sheet metal tube 8, secured as indicated to the front end of casting 5. This tube projects forwardly and terminates with an open end surrounded by a deflector 8', which end is adapted to be inserted through the wall of the combustion chamber of a heating apparatus. The rear end of conduit 1 is closed. The fan I delivers air downwardly through the outlet 4' into the air conduit 1 and thence forwardly through the conduit to mix with the spray of atomized oil.

The spray of atomized oil is produced by one or the other of two oil-atomizing nozzles 9 and ill. The nozzle I0 is broken away in Fig. 2 but both nozzles are shown in Fig. 5. The nozzles 9 and ill have supply conduits ii and I2, which are adapted for connection one at a time to an ity of one gallon per hour and the nozzle l may have a capacity of one and one-half gallons per hour.

Preferably, a so-called turbulator is provided near the outlet end of tube 8. This comprises an annulus 13 having a circular series of inwardlyprojecting spiral vanes II which serve to whirl the air Just prior to its delivery to the spray of atomized oil.

Each oil nozzle (Fig. 6) ismounted in the outer end of a hollow casing l5, which may, as shown, contain a strainer 1'5. These nozzle casings are mounted, as shown in Fig. 5, in holes in a bridge piece l1 and are held thereto, as by set screws iii. The two nozzles are preferably arranged with their axes in forwardly converging relation for the purpose of centralizing the oil spray, produced by each, relatively to the air conduit 1. The ends of the bridge piece l1 are mounted on two laterally-spaced, parallel rods 19 and are fixed thereto as by set screws 20. The forward ends of the rods 19 are suitably fixed as indicated, at diametrically opposite points to the annulus 13 which has a slidable engagement with the inner peripheral wall of tube 8. The rods l9 extend rearwardly through air conduit 1 and terminate with outwardly turned ends 2!, adapted to engage one in each of two openings formed at diametrically opposite points in the inner peripheral wall of the air conduit near its rear end. Such end is normally closed by a plate 22, secured as indicated in Fig. 3 to member 1.

The mixture of air and oil is preferably ignited by an electric spark, produced by means later to be described, between a pair of electrodes 21. A second bridge piece 23, secured at its ends, as by set screws 24, to rods l9, supports two insulators 25, which are held in place by set screws 26. These insulators support, one in each, the electrodes 21.

The assembly of nozzles 9 and ID, the turbulator I3 and electrodes 21 may be withdrawn from the air conduit 1 as a unit for the purposes of adjustment, inspection or repair. Referring to Fig. 5, the oil conduits l l and 12 are first disconnected at the compression couplings I I and 12. After plate 22 is removed, the wires are disconnected from the electrodes 21. Then the rods I9 may be drawn inwardly toward one another to withdraw the ends 2| from their openings, after which the rods may be pulled rearwardly out of conduit 1 carrying therewith the nozzles, turbulator and electrodes, all in, proper working relation. The assembly may be easily replaced and the parts will be properly located in conduit 1 when the ends 2| of rods l9 are engagedin their openings. The wires are then connected to the electrodes, the oil conduits II and I2 reconnected and plate 22 fastened in place.

Referring next to Fig. 3, the pump which supplies oil to the atomizing nozzles is shown at 2. This pump and the fan I are driven by an electric motor '3. The casing of the motor'3 is suitablyfixed, as indicated to one side face of the fan housing 4. In the opposite side face of this housing is the air inlet opening -28 to the fan i. Integral with and projecting from the last-named side face are two arms 29 (Fig. 8), one on each side of the inlet 28, and the outer ends of these arms are integrally connected-by a cross bar 35,

to which the oil pump 2 is secured, as by cap screws 30'. with its drive shaft 3| extending toward and coaxially of the shaft 32 of the motor. The fan i has a hub 32 which is suitably fixed directly to shaft 32. The pump 2, however, is preferably connected to the motor shaft through the intermediary of a'speed-responsive clutch, the driving and driven elements ofwhich are indicated at 34 and 35. The driving element 34 is connected by a flexible coupling 36 to the hub 33 of fan I and the pump shaft 31 is fixed as indicated, to the driven clutch element 35. The clutch 34, 35 enables the motor 3 to be started up without the load of the pump 2 and enables the motor and fan to attain considerable speed before the oil pump is started. also, on stopping, the oil pump stops before the fan and motor. The arrangement is like that of Logan Patent No. 1,985,934, granted January 1, 1935, to which reference is made for a complete disclosure of the clutch if necessary or desired.

The air inlet 28 of the fan is controlled by an air valve in the form of an annular shutter 31, (Figs. 3 and 8), the central opening of. which receives the clutch elements 34 and 35. Fixed to the shutter is a nut 38 (Fig. 3) which is threaded on a screw 39. This screw has smooth cylindrical portions near its ends which portions are rotatably and slidably supported in bearings 40 and 4|, respectively, located in fan housing 4 and cross bar 30. The screw is bodily movable in the direction of its axis to carry the shutter 31 from a position suitable for low firing rate operation to a position suitable for high firing rate operation. The screw has a shoulder 42 which is adapted to abut the adjacent end face of bearing 40 and limit the axially inward movement of the screw and thus define the low firing rate position of the shutter. Such position may be variedby rotating screw 39. Sliding movement of the latter in the opposite direction is limited by a second screw 43, with the inner end of which a circumferentially grooved collar 44, fixed 0n screw 39, is adapted to abut and define the high firing rate position of the shutter 31. The screw 43 is threaded in a nut 45, fixed to a circumferentially-fianged annular member 46, which in turn is fixed, as by screws 45', (Fig. l) to cross bar 30. By turning the screw 43 the high firing rate position of shutter 31 may be adjusted.

The air shutter is shifted from one firing rate position to the other by means of a lever 41 (Figs. 3 and 8), the upper end of which is engaged in the groove in collar 44. This lever extends downwardly, beingofi'set, as shown in Fig. 8, to clear the hub and shaft 3| of the pump 2, and into a groove 48 in a block which is fixed, as by the cap screws 50 (Figs. 5 and 9) to the tubular 1ower part of the casting 5. A pin 5| fixed in the block 49 as indicated, serves as the fulcrum for the lever. The lower end of the lever 51 (Fig. 9) is pivotally connected by a pin 52 to the outer end of a piston rod 53 having on its inner end a piston 54, slidably mounted in a cylinder 55, formed by a hole drilled into one face of the block 49. An annular nut 56 is threaded in the outer end of the cylinder and'slidably receives rod 53. A spring 51, coiled around the rod and acting between the nut and piston 54, tends to hold the piston at the inner end of its stroke and thus the air shutter 31 in its high firing rate position. Liquid under pressure, when admitted to the inner end of the cylinder 55 will force the piston 54 outwardly, compressing spring 51 and moving lever 41=to carry the shutter 31 into its low firing rate position.

The block 49 (Figs. 1, 3, 9 and 10) also serves to support two solenoid valves which are used to control the flow of oil to the nozzles 9 and I8 and to the motor cylinder 55. These valves, designated generally as 58 and 59, are mounted one above another in holes qbored laterally through the block 49. These valves are standard articles available in the market. Each is mounted in the same way and the mounting of only one, such as 58, will be described. Valve 58 (Fig. 10) includes a cylindrical end member 68 to which is fixed one endof a tube 8|, which is of non magnetic material and the other end of which has fixed to it a core 62 of magnetic material; The solenoid coil 63 encompasses the tube 8|. mercial form of solenoid valve includes a jacket surrounding coil 63. In this case, the jacket is removed because the block 49 will do its work.

The inner end of member 88 fits into one end of.

the solenoid valve receiving hole in block 49 and a shoulder 84 on such end abuts block 49. A cover 65 fits over the core 62 and has a part to fit the other end of said hole in block 49 anda shoulder to abut the block. A nut 61, threaded on core 82,binds the parts together, clamping the shoulders 84 and 88 against opposite face", of block 49. The latter has a vertical passage 88 (Fig. 9) therein which intersects both the valve-receiving holes which house the solenoid coils. The wires for these coils may be brought in through the passage 88 and a conduit, shown in part at 89, connected thereto. The interior of tube 6| serves as an oil chamber 18 and also as a housing for theplunger 1| of the solenoid. This plunger also serves as a valve, oneof its end faces being held by a spring 12 against a valve seat 13 on the end member 68 and the opposite end face being adapted to engage a valve seat 14 on core 82 at the opposite end of the oil chamber 18,when the solenoid coil 83 is energized. The oil chamber of valve 59 .is marked 15, its coil 18, its valve plunger 11 and the right and left hand valve seats as 18 and 19, respectively.

The oil pipe connections, ,as they are actually made, are shown in Figs. 3, 5, 9 and 10. For convenience in tracing the oil circuits and understanding the operation, these connections have also been shown' diagrammatically in a single view, Fig. 11, in relation to the valves and pump and nozzles. The oil conduit H (Fig. 9), carrying the low firing ratenozzle 9, is connected to a passage 88 leading through the valve seat 18 of valve 59. The conduit l2 (Figs. 9 and 10), carrying the high firing rate nozzle, is connected to one end of a passage 8| (see also Fig. 1), extending through block 49, and the other end of this passage is connected by a pipe 82 (Fig. 10) to a passage 83, extending through the valve seat 14 of valve 58. A passage 84, extending through the valve seat 13 of valve 58, is connected by a pipe 85 to the oil chamber of valve 59. A pipe 86 (Fig. 9) connects chamber 15 to the motor cyl- A passage 81 (Fig. 10), extending inder 55. through valve seat 19 of valve 59, is connected to a pipe 88, which as shown in Fig. 1, extends to the suction pipe 89 that connects pump 2 with the fuel supply tank (not shown). The outlet of pump 2 (Fig. 1) is connected to one end of a pipe 98 the other end of which as shown in Fig. 10 connects with the oil chamber 18 of valve 58.

The oil pump 2 includes a combined cut-off and pressure-regulating valve, housed within the pump casing. This valve is shown diagram- The standard commatically in Fig. 11 by a piston 9|, pressed by a spring 92 against a valve seat 93, through which extends the outlet passage, which is connected to pipe 98. Liquid is forced by pump 2 into a chamber 94 and, when this liquid reaches a predetermined minimum pressure, say 85 pounds per square inch, piston 9|. is moved to the left to allow oil to flow into pipe 98. When the oil in chamber 94 attains a predetermined maximum pressure, say 100 pounds per square inch, piston 9| will be moved to the left far enough to uncover a port 95 and allow oil from chamber 94 to fiow through port 95 into a chamber 98, which is connected to the suction side of pump 2. An example of 'one oil pump suitable for the purpose will be found in Wahlmark Patent No. 2,232,983, dated February 25, 1941, to which reference is made for a complete disclosure of the pump with I its pressure-regulating and by-pass valves, if necessary or desired.

The operation of supplyingfuel and air to the burner at different rates will best be understood from the diagram of Fig. 11. With both the solenoids 63 and 16 deenergized, the valves 1| and 11 will be held against the seats 13 and 18, respectively, whereby the passage 84-is closed' to prevent the oil, suppliedby pump 2 by way of pipe 98 to chamber 18, from flowing to chamber 15 and thence by pipe 86 to the motor cylinder and also to prevent fiow from chamber 15 to passage 88 and thence by pipe I l to the low firing rate nozzle 9. Operation of the latter and the airshutter-operating motor are thus prevented. However, the valve 1| has opened the passage 83 of valve 58 and oil, supplied by the pump to chamber 18, can fiow through passage 83, pipe 82, passage 8| and pipe I2 to the high firing rate nozzle l8. At the same time, valve 11 has uncovered the passage 81 of valve 59 so that the inner end of cylinder 55 is connected by pipe 88, chamber 15, passage 81 and pipe 88 to the suction side of pump 2. The spring 51 will hold the piston 54 at the inner end of its stroke and.

through lever 41, hold the air shutter 31 inthe passages 84 and 88 of valves 58 and 59, respectively, will be opened. Oil, supplied by pump 2 to chamber 18, can fiow by way of passage 84 and pipe to chamber 15 and thence by way of passage 88 and pipe H to the low firing rate nozzle 9. Also, oil from chamber 15 of valve 59 can fiow by way of pipe 88 into cylinder 55, thereby forcing piston 54 to the left and through lever 41 moving the air shutter 31 to proper position for low rate firing.

It will be noted that the air shutter is always in its position of greater opening, when the burner is started. The solenoids 63 and 18, as will later appear, cannot be energized until the burner motor starts. If they are then energized, as they would be for low firing rate operation, the valves 1| and 11 will open passages 84 and 80. respec-v short time before oil is emitted from nozzle 9 and 7 before oil is admitted to cylinder to shift the shutter 31 to its low firing rate position. Thus, whenevbr the burner is set to operate at the low firing rate, and for the greater part of the heating season, it would be operating at such rate, the burner will start up with a lean mixture of air and oil which. is very desirable.

Also, when the burner is stopped, while set for low firing rate operation, the solenoids 03 and 16 will be deenergized immediately when the circuit to the burner motor 3 is opened. On deenergization of the solenoids, the valves 1| and 11 will be moved with a snap action by their springs and the fuel conduit to the nozzle 0 will be closed at two places by these valves considerably before the burner cut-oil? valve 9| can close. An almost instantaneous, quick, sharp and double cut-off of the oil iiow to the nozzle results. The motor 3 and fan I will coast for awhile to keep some air moving through conduit 1 but the oil flow from nozzle 0 will be stopped instantly, when the circuit to motor 3 is'opened. v

Ii. the double cut-off of the oil flow to nozzle 9 is not desired, the pipe 85 can be made to connect with p'assage 80, as shown in Fig. 12. Then, the flow of oil to nozzle 9 will be controlled only by valve 1| and the valve 11 will be used to control the supply of oil to the motor cylinder 55. With this arrangement, on a, failure of solenoid coil 16, while the burner is set for operation at a low firing rate, the burner can continue in operation but with a lean mixture because the shutteroperating cylinder 55 is cut off from the supply of pressure fluid by the closing of valve 11.

If the solenoid coil 03 fails, while the burner is set for operation at the low firing rate, the burner will operate at the high firing rate in the emergency.

As shown in Figs. 1, 3, 5, 8, 9 and 10, the block 49 with-its solenoid valves 58 and 59 and some of I the pipe connections are enclosed by a sheet'metal hood 91. This hood (Fig. 1) is held to the lower part of casting by screws 98. Fixed to the top of the hood (Fig. 8) are two clips 99 and I00. A

part-cylindrical piece of sheet metal IOI (Fig. 3) encloses the space between the tan housing 4 and end member 46, resting at its ends on the flanges I02 and I03, formed on such housing and member respectively. This part IOI (Fig. 8) has along one edge an out-turned lug I04 perforated to receive a hook I05 on clip 99. Along the other edge of member IOI is another lug I06, which is held by a screw I01 to clip I00. Air may enter inside the member .IOI to reach the air inlet 20 by means of the space between the lower edges of the member and by means of slots in the member indicated at IOI7 in Figs. 1 and 8.

Since the air shutter is moved back and forth frequently by the lever 41, it is desirable that the nuts 38 and 45 besecurely held to their respective screws 39 and 43. For this purpose, each nut may 8 mg terminals III and H2; a switch Ill whichis for a purpose later to be described and which may now be assumed to be closed; and the switch II4, which controls the motor 3 and ignition means and which is closed by a room thermostat switch I I5 on a demand for heat from the burner. This circuit may be traced as follows: from one supply wire IIO, terminal 1, wire IIO, switch II4, wire H9, terminal I20, wire I2I, switch II3, contact I22, wire I23, terminal I24, wire I25, selector switch terminals H2 and III, wire I20, solenoids 63 and 10 and wire I21 to the other supply wire I20. As shown, the selector switch H0 is set for high firing rate operation and its terminals III and H2 are disonnected. Consequently, when the burner is started by closing the switch II4,

the solenoids 03 and 10 will not be energized and moved into positions for low firing rate operation.

According to some features of the invention,

the selector switch IIO may be turned manually. Or, it may be turned by a thermostat, such as that conventionally indicated at I30. This thermostat may be placed at various locations as desired. As one example, it may be located outdoors and constructed to move the selector switch to high firing rate position, when the outdoor temperature is at 20 Fahr. or below, and to move the switch to low firing rate position, when the outdoor temperature is above 20 Fahr.

The circuit for the burner motor and the ignition means, will next be described. The ignition means includes a transformer having primary and secondary coils I3I and I32, respectively, the secondary coil being connected by wires I33 and I34 to the spark electrodes 21. The primary coil I3I is connected in parallel with motor a H6, terminal II1, wire H8, switch II4, wire H9,

terminal I20, wire I35 to the motor 3 and primary I3I and thence by wire I30 to supply wire I20.

In a burner of the kind described, where one nozzle may operate repeatedly over long intervals and the other may lay idle, the idle nozzle may be constructed, as shown in Fig. 4, in two parts which have a tongue and groove engagement I08 to make them turn in unison and which are pressed apart by a spring I09. The two nut sections are thus pressed against opposite faces of the threads on the'screw to provide sufiicient frictional engagement between the nut sections and screw to prevent accidental turning of the nut sections due to vibration.

' Referring now to the means for controlling the solenoid valves, in Fig. 13, the solenoids 03 and 10 are shown as connected in parallel and included in an electrical energizing circuit, which includes a mercury tube ,selector switch I I0, havbecome carbonized and not be operative, when it is finally selected for operation. To reduce the likelihood of trouble from this source, this invention provides means, whereby each nozzle will be used during each cycle of operation of the burner. For example, if the selector switch "0 is set for the high firing rate, then when the burner is started, the low firing rate nozzle 0 will first be operated for a short period, after which the high firing rate nozzle I0 will be brought into play. And if the burner is set for low firing rate operation, it will start up at the high firing rate and, after a brief interval, the low firing rate nozzle will be brought into action. To accomplish this an alternate energizing circuit is provided for the solenoids 63 and 16, which circuit is controlled by the described switch H3, and an auxiliary selector switch, which moves with the primary selector switch and which may be and preferably is incorporated in the same tube, closed by the same mercury I28 and tilted by the same means. As shown, the auxiliary switch has a terminal I31 connected by a wire I31 to a terminal I38 and thence by a wire I38 to a second contact I40 of switch I I3 and a terminal I42 connected to wire I 26. The auxiliary selector switch operates reversely to the main selector switch and closes and opens. when the main selector switch opens and closes respectively. Accordingly, when the switch H3 is moved from contact I22 to contact I40, a circuit will be closed to the solenoids as follows: -from supply wire II6,

terminal II1, wire 8, switch II4, wire II8, ter- -minal I20, wire I2I, switch II3, contact I40, wire I 38, terminal I38, wire I31, auxiliary selector switch terminals I31 and I42 which are connected by the mercury I28, wire I26, solenoids 63 and 16, and wire I21 back to supply wire I28. If the primary selector switch H is set for the low firing rate so that its terminals III and I I2 are connected by the mercury I28, then the terminals I31 and I42 of the auxiliary selector switch are disconnected. Accordingly, when the burner starts, the switch I I3 when moved to contact I40 will not energize the solenoids and the valves will remain in their high firing rate positions.

The switch H3 is arranged to close, when the room thermostat II closes to start the motor 3 and the ignition means, and to open when combustion at the burner has been established. Thus, on starting the burner, the switch I I3 first moves to engage contact I40 and this causes the nozzle, which is not selected by the primary selector switch IIO, to be operated for a moment. Then, after combustion occurs, the switch II3 moves back to engage contact I22, re-establishing the normal energizing circuit for the solenoids and causing the nozzle selected by switch 0 to operate.

To efiect operation of switch I I3 in the manner described, I utilize a standard form of oil burner control instrument, which is intended for use ment is that'shown within the dot-dash rectangle.-

The switch II3 was originally intended to control the ignition circuit, closing it, when the contact I40 is engaged and opening itafter combustion has been established. The contact I40 was originally connected to terminal H 1 and the switch I I3 was originally connected to terminal I38 and thence to the primary I 3| of the ignition transformer." The switch H3 is part of a relay which includes three other switches I 43, I 44 and I45, actuated by the electromagnet I 46, as indicated. This relay is actuated to close the three last-named switches and move switch '3 to engage contact I40, when the room thermostat calls for heat. After this relay is actuated, another relay is actuated almost instantly by its electromagnet I41 to close the motor switch II4 and three other switches I48, I48 and I50. After combustion occurs, a stack thermostat, shown conventionally at I 5I causes a pair of contacts I52 to separate and open the circuit to electromagnet I46, whereby the first relay drops out, opening switch '3: I

The detailed way in which the aforesaid control operates will next be described. The room thermostat switch includes a bimetallic thermostat blade I53; two fixed contacts I54 and I55,

i 10. which are engaged successively by the blade in the order named on a demand for heat: and an electric heating coil I56, which at certain times is energizedto heat blade I53 andexpedite its switch opening movement. The contacts I54 and I56 are connected by wires I51 and I58 to terof coil I61 and the minals I58 and I60, respectively, The blade I63 is connected by a wire I'6I to one terminal of coil I56 and the other terminal of the latter is connected by a wire I62 to a terminal I63. The terminal I58 is connected by a wire I64 to one terminal of the secondary I65 01' a transformer. The other. terminal of this secondary is connected by a wire I66 to one terminal of a heatactuated time switch I61, heated by an electric heating coil I 61', when the latter is energized. The other terminal of switch I61 is connected by a wire I68 to one terminal of electromagnet I46 and the other terminal of the latter is connected by a wire I68 to one of the contacts I52. The other contact I52 is connected by a wire I10 to the contact of switcht'l44. This last-named contact I52 is connected to one of a second pair of closed contacts "I. The other contact "I is connected by wires I 12 and I13 to one terminal other terminal of the latter is connected by wires I14 and I15 to terminal I60. A wire I16 connects wire I12 to the contact of switch I45. A wire I11 connects the contact of connected as indicated at I85. All the switch I 43 to one of a pair of open contacts I18 and such contact is. also connected by a wire I18 to one terminal of electromagnet I41, the other terminal of which is connected by a wire I80 to 7 wire I68. The other contact I18 is connected by a wire I8I to the contact of switch I50. The contact of switch I48 is connected by a wire I "to the Junction ofwires I14 and "5., The contact of switch I 46 is connected by a wire I83 to the terminal I63. The switches I48, I48 andI50 are electrically connected as indicated at I84. 80, also the switches I43, I44 and I45 are electrically of the two relays, except I I3 and I I4 are arranged in low voltage circuits supplied from the secondary I of atransformer I 66, the primary I81 of which is connected by wires I88 and I88 to terminals I I1 and I'80, the latter being connected by a wire I 8I to supply wire I28. The transformer is thus continuously energized.

In the operation of the control instrument described, on a demand for heat, the blade I53 first with contact I 54 and then withconta-ct I55. As soon as both contacts are engaged, a circuit to the electromagnet I46 is closed which circuit maybe traced as follows:

from the right hand terminal of secondary I65 by wire I64, terminal I58, wire I51, contact I54, blade I53, contact I55, wire I 58, contact I 60, wires I15 and I14, heat coil I61. wires I13 and I12, engaged pairs of contacts "I and I52, wire I68, electromagnet I46, wire I68, time switch I61 I and 'wire I66 to the other terminal of seconadry I65. The electromagnet I46, being energized, the first relay pulls in, closing switches II 3, I43, I44' and I45. Switch II3 will reverse the normal connections to the solenoids 63 and 16 as heretofore described, so as to actuate the unselected nozzle when the burner motor'starts. The closing of switches I43 and I45 closes a circuit to the electromagnet I41 of the other relay, which circuit may be traced as follows: from the right hand terminal of secondary I65 by wire I64, terminal I58, wire I 51, contact I54, blade I 53, contact I 55, wire I58, terminal I60, wires I15 and I14, heat coil I61, wires I13 and I16, switch I45, connecswitches tion I85 to switch I43, switch I43, wires I11 and I19, electromagnet I41, wires I80 and I68, time switch I61 and wire I66 back to the left hand terminal of secondary I65. The switches I44 and I45 close a shunt across the contacts I1 I, which shunt may be traced as follows: from left hand contact I1l by wire I10, closed switch I44, connection I05, closed switch I45 and wires I16 and I12 to the right hand contact I1I.

When the electromagnet I41 became energized, the second relay pulled in, closing switches H6, I40, I49 and I50. The closing of switch I I4 starts the burner motor 3 and energizes the ignition transformer to produce an ignition spark across electrodes 21. Also, the solenoids 53 and 16 will be energized if the selector switch H is set for high firing rate operation. If combustion occurs, as it should, the stack thermostat I5I will be actuated to move the pairs of contacts I52, Ill and I18. If combustion does not occur within, say 90 seconds, the heating coil I61 will have moved the bi-metallic blade of time switch I01 to open the same, thereby opening the circuit to the electromagnets I46 and I51 and causing both relays to drop out and the motor and ignition means and solenoids 63 and (if previously energized) to be deener'gized.

Assuming that combustion occurs, the stack thermostat I5I will first cause the contacts I15 to engage, then the contacts III will be caused to disengage and finally the contacts I52 will be caused to disengage. The closing of the contacts I18 will shunt out the electric heating coil I61 and thus prevent the time switch from opening. This shunt may be traced 'as follows: from the upper terminal of heating coil I61, by wires I15 and I02, closed switch I59, connection I84 to switch I50, closed switch I50, wire I6I engaged contacts I10, wire I11, closed switch I43, con.-

nection I05 to switch I45, closed switch I45, and- Wires I16 and I13 to the lower terminal of the heating coil. An alternate circuit to electromagnet I51, excluding the heat coil I61, and the first relay, is now provided as 'follows: from the right hand terminal of secondary I65 by ,wire I64, terminal I59, wire I51, contact I56, blade I53, .contact I55, wire I58, terminal I60, wires I15 and I02, closed switch I49, connection I84 to switch I50, closed switch I50, wire I8I, engaged contacts I10, wire I19, electromagnet I41, wires'I80 and I68, time switch I61, and wire I66 to the left hand terminal of secondary I65. The electromagnet I41 of the second relay will now remain energized after the first relay drops out. The switch I40of the second relay closes a second and parallel branch of the holding circuit for electromagnet I41 just described. This second branch starts from switch I49, through the connection I64 to switch I48, closed switch I48, wire I83, terminal I63, wire ISL-thermostat heater I56, wire IIiI, blade I53 to Contact I55. This branch will carry practically no current because its resistance is high due to coil I55,, as compared to the other branch I82, I15, I60, I58 and I55 which has extremely low resistance: However, when the other branch is opened, as later described, all the current will flow through the second branch and energize coil I56. After the stack thermostat I5! has closed the contacts I13, it opens contacts ill but this has no immediate effect because of the closed shunt described, which maintains the circuit through switches I44" and I45. Then, the

stack thermostat separates the contacts I52 and this opens the circuit to electromagnet I46 of the first relay, causing it to drop out and open the switches II3, I43, I44 and I45. Switch H3 changes the circuit to solenoids 83 and 16, causing them to be energized or deenergized accordingly asthe selector switch H0 is set for low or high firing rate operation, respectively. The opening of switches I44 and I45 opens the shunt across the heating coil I61 and opens the circuit thereto so that the contacts "I when subsequently reengaged, will close a circuit to this heat coil.

The burner continues in operation with only the second relay pulled in. 'The circuit tor the electromagnet I51 of this relay includes the engaged contacts I16. Should combustion fail, these contacts will be separated by the cooling of the stack thermostat and the circuit to electromagnet I41 will be broken, causing the second relay to drop out, opening the switch H4 to stop the motor 3 and the ignition means, and also to open the switches M8, I49, and I50. As the stack thermostat I5I continues to cool, the contacts I62 and the contacts I11 will be engaged. This occurs in about a minute after contacts I10 are separated. The contacts I52 and I'll when engaged start up the motor in the manner first described, the first relay pulling in and being followed by the pulling in of the second relay. The safety time switch I51 and its heat coil I51 are in the circuits to both these relays so that if combustion is not established in 90 seconds, the switch I51 will open and stop the burner until this switch is again closed which usually requires manual resetting. If combustion does occur the first relay will drop out as before described and the second relay only will remain pulled in.

The burner continues in operation until the demand for heat is satisfied. The initial rise in room temperature will cause the blade I53 to move to the right and disengage from contact I55 while remaining in engagement with contact I55. One branch of the circuit, including Wire I56, terminal I and wires I15 and I82, to electromagnet I51 is thus broken and all the current must now flow through the other branch including switch I48, wire I03, terminal I63, wire I52, coil I56 and wire I6I. Thus, the heating coil I56 will be energized to expedite the heating of blade I53 and the breaking of its engagement with contact I54. The arrangement is that of the customary anticipating thermostat, the

burner being stopped a little before the desired 7 room temperature is attained. This prevents the substantial overruns of temperature that frequently result when the heater I56 is not employed.

Another feature of the invention has to do with an. arrangement whereby it the selected nozzle fails to operate, the other nozzle will automatically be brought into operation. Such arrangement is shown diagrammatically in Fig. 14. In this figure, the circuit to the burner motor 3 and the ignition means is the same as in Fig. 13 and it is controlled, as before, by a switch I14, closed by a relay I41 on a demand for heat from the burner, as evidenced by the room thermostat H5. The selector switch H0 and the reversing switch II3 are retained and function as before to control the solenoids 63 and 16. However, there is interposed between these solenoids and the selector switch 0 a normallyclosed time switch I32, which is heat-actuated from an electric heating coil I 93 and is adapted-;.to open in a predetermined time, say 20 seconds. One terminal of switch I92 is connected 13 by a wire I94 -'to the interconnected terminals III and I42 of the switch '9. The other terminal of switch I92 is connected by a wire I95 to I93 and I91, will be held opened and closed, re-

spectively, by spring-actuated latches 299 and 2M.

a wire 292 to a switch 293. The heating coil I91 has one end connected to wire I99 and has the other .end connected by a wire 294 to one terminal of a switch 295. The other terminal of switch 295 is connected by a wire 291 to terminal I99 and the other terminal of switch 293 is connected by a wire 296 to the Wire 291. The switches 293 and 295 are adapted to be opened by the stack thermostat II in a short time after combustion occurs, say seconds. This stack thermostat, as before, serves to close a pair of contacts I18, then open a pair of contacts Ill and finally open a pair of contacts I52. In addition, this thermostat is made to open a pair of contacts 298. These contacts open a very short time after combustion occurs, say flve seconds,-

and before any of the other pairs of contacts are actuated.

The switch H3 is actuated to engage contact I49 by means of the relay I46. The motor switch H4 is actuated by a relay I41, together with the switches I48, I49 and I59, but the connections are somewhat different as will now be described.

One terminal of relay coil I46 is connected by a wire 299 to one terminal of the secondary I65 and the other terminal of the latter is connected by a wire 2I9 to the terminal I 59. The other terminal of relay coil I46 is connected by a wire 2 to a spring contact finger 2I-2 which is fixed at one end and has its contact in engagement with a spring contact finger 2I3, which is fixed at one end and connected by a wire 2| 4 to one of the contacts 298. The other contact 298 is connected by wires 2I5, 2I6 and 2I1 to the terminal I69. Accordingly, when the room thermostat II-5 calls for heat and its contacts I54 and I55 are connected by blade I53, a. circuit will be closed to relay coil I46, as follows: from the right hand terminal of secondary I65 by wire 2I9, terminal I59, wire I51, contact I54, blade I53, contact I55, wire I58, terminal I69, wires 2", 2I6 and 2I5, engaged contacts 298, wire 2I4,

engaged contact fingers 2| 3 and 2I2, wire 2, relay coil I46 and wire 299 to the other terminal of secondary I 65. This circuit will be opened, when the contacts 298 separate, shortly after combustion occurs.

One terminal of relay coil I "is connected by a, wire 2I8 to wire 299 and the other terminal is connected by a wire 2I9 to one terminal of the switch I61. The other terminal of switch I61 The heating coil I93 has one end connected to wire I94 and has the other end connected by contact of switch I59. The'other contact "I is connected by-a wire 224 to wire 2I6. The other contact I18 is connected by a wire 225 to switch I61. The contact of switch I49 is connected by a wire 226 to wire 2| 1. The contact of switch I48 is connected by a wire 221 to terminal I63.

When the room thermostat H5 calls for heat and its blade I53 connects the contacts I54 and I55, a circuit is closed to the relay coil I41. This circuit may be traced as follows: from the right hand terminal of secondary I65 by wire 2I9, terminal I59, wire I", contact I54, blade I53,

contact I55, wire I58, terminal I69, wires 2",

wire 2I9, relay coil I41, and wires 2I8 and 299 to the left hand terminal of secondary I65. Thus, the relay I41 pulls in simultaneously with the relay I48 and thereby closes the switch II4 to start the motor 3 and the ignition means and also closes the switches I48, I49 and I 59. When the switch I 59 closes, it connects with wire 223 and thus with one of the contacts I18 and, when switch I49, closes, it connects with wire 226 for the purpose of establishing an alternate circuit to solenoid I 41, which circuit will be completed when the contacts I18 engage, following combustion. Such circuit may be traced as follows: from the right hand terminal of secondary I65 by wire 2I9, terminal I 59, wire I51, contact I54,

blade I53, contact I55, wire I59, terminal I69,-

wires 2" and 226, closed switch I 49, connection I64 to switch I59, closed switch I59, wire 223, engaged contacts I16, wire 225, switch I 61, wire 2I9, coil I41 and wires 2I8 and 299 to the left hand terminal of secondary I65. The closing of the described circuit by the engagement of the contacts I18 will shunt out the heater-coil I61 lay I41 to drop out and stop the burner. On 00- currence of combustion, contacts 296 disengage first in say five seconds, followed by the opening of switches 293 and 295 in say 10 seconds, followed by the engagement of contacts I18,- and is connected by a wire 229 to one terminalof the heating coil I61 and the other terminal of the latter is connected by a wire 22I to one of the contacts I52. The other contact I52, which is also connected to one of the contacts "I, is connected by a wire 222 to one of the contacts I18 and the latter is connected by a wire 223 to the then by the disengagement of contacts I1I and then by the disengagement of contacts I52. The closing of switch I48 closes a second and parallel branch in the circuit to the relay coil I 41. .This

- branch starts at switch I59 and extends through connection I84, closed switch I48, wire 221, terminal I63, wire I62, thermostat heater I56, wire I-6I, and blade I53 to contact I55. This branch will carry practically nocurrent because its resistance is high due to coil I56, as compared to the other branch comprising switch I49, wires 226 and 2", terminal I69, and wire I59, which has extremely low resistance. the last described branch is opened, when the thermostat blade disengages from contact I55, all the current will flow through the branch which includes coil I56,"whereby the latter will heat the blade I53 and accelerate its movement to the right, causing it to disengage from contact I54 and stop the burner somewhat earlier than it would otherwise do. 1

The spring contact finger H2 is actuated by swung counterclockwise and clockwise, when the However, when relay I48 respectively pulls in and drops out and this lever through a rod 229 engages the finger 2I2 andcontrols its movement. Similarly, the

229 and 232 move to the right, allowing both fingers to swing back into unfiexed position, while maintaining their contacts engaged. This condition is illustrated in Fig. 15. When relay I48 drops out in response to the separation of contacts 208, the rod 229 will be moved to the left, flexing spring finger Zia to the left and carrying its contact out of engagement with the contact on finger 2I9. This condition is shown in Fig. 16. This arrangement provides a second break in the circuit to relay I48, whereby if the contacts 209 should engage, shortly after their separation, the relay I40 cannot be energized. When the relay I41 drops out, the rod 292 is moved to the left, flexing spring finger 2I3 to the left far enough to reengage its contact with the contact on finger BIZ. This condition is indicated in Fig. 14.

If following the energization of the relays I48 and I41 combustion does not occur, the heater I61 will in a predetermined time, say 90 seconds,

- cause switch I61 to open and this will open the circuit to relay I91, causing the latter to drop out and stop the burner by opening switch H4. This safety switch I61 generally has to be manually reset before the burner can operate. If the burner starts and a failure of combustion occurs later, then the stack. thermostat ital starts to cool and the first action is to separate contacts I16, which opens the circuit to relay I91. and causes immediate stopping of the burner. Continned cooling of the stack thermostat causes the contacts 208 to reengage, then the switches 209 and 895 to close, then the contacts I52 to reengage and finally the contacts Hi to reengage. The reengagement of the pairs of contacts HI and I52 occurs in about one minute after the contacts I18 separate and provides a scavenging period. With the room thermostat H5 still closed, the relays I46 and I41 will pull in and the burner will start up as before and, if combustion does not occur in 90 seconds, the heater I61 will open switch I61 and stop the burner until the switch I81 is manually reset.

The operation of the system shown in Fig. 14

- will next be described. With the switch IIIl positioned as shown, on a demand for heat from the burner, the room thermostat H5 will close, causing relays I46 and I41 to pull in, as described, and move switch H8 to contact I40 and close switch H4 to start the motor 3 and energize the ignition transformer. A circuit is established to the solenoids 63 and 16 as follows, from supply wire IIB, terminal II1, wire II8,

closed switch H4, wire H9, terminal I20, wire I2I, switch II3, contact I40, wire I39, terminal I38, wire I31, terminal I31, mercury I29, terminal I42, wire'i94, switch I92, wire I95, solenoids 63 .and 18, and wire I21 back to supply wire I28. The solenoids, being energized, the low firing rate nozzle 9 is connected to operate. At the same time, the heaters I93 and I91 are connected in the following circuits. That for heater I99 is the same as for the solenoids through wire I94 and thence it extends through heater I89 and wire 202 to switch 208, and thence by wires 208 and. 201, terminal I90 and wire I9I to supply wire I28. The energizing circuit for heater I91 is as follows: from supply wire II8, terminal II1, wire II8, closed switch H4, wire III), terminal I20, wire .I99, heater I91, wire 204, switch 205, wire 201, terminal I90 and wire I9I to supply wire I28.

If combustion occurs, the contacts 208 will be separated by the stack thermostat IBI followin the first relatively small rise in temperature in the stack, say in five seconds, thus opening the circuit to relay I48, which drops out causing switch II3 to engage contact I22. As relay I 46 drops out, the finger M2 is moved out of engagement with finger 2I9. The primary energizing circuit to the solenoids is then open at switch IIO, the circuit being as follows: supply wire II6, terminal II1, wire II8, closed switch us, wire H9, terminal I28, wire I, switch H8, contact I22, wire I28, terminal I24, wire I25, terminal H2, terminal III, wire I94, switch I92, wire I 95, solenoids 63 and I0, and wire I21 back to supply "wire I28. Accordingly, the solenoids t3 and It will -be deenergized, causing the high firing rate nozzle In to be connected for operation. The heater I93 will be deenergized because its circuit is open at the selector switch III] but the heater I91 will continue to be energized. If the nozzle iii operates, the rise in temperature, following combustion, will cause stack thermostat Ifii to open the switches 209 and 205. This should occur in a few seconds after contacts 208 have separate'd, say from 2 to 5 seconds, or from 7 to 10 seconds following the occurence of combustion. The heater I91 will thus be cut out of circuit, preventing switch I98 from closing. Then the contacts I18 will engage and shut out the heating coil I91, preventing the safety switch I61 from opening. Then the contacts I1I will separate and finally the contacts I52 will separate. The burner is now in running condition and will continue in operation until the room thermostat H5 opens because the demand for heat is satisfied or until a failure of combustion occurs.

If the burner shuts down in the normal way by the opening of room thermostat M5, the relay I41 will drop out, opening switch H4 to stop the motor 8 and the ignition means and opening switches I48, I49 and I50. .As relay I41 drops out, it moves the finger 2I3 into engagement with finger 2 I2. The contacts I19 separate very quickly as the first cooling of the burner thermostat I5I occurs. As the thermostat I5I continues to cool, the contacts 208 will be reengaged, the switches 203 and 205 will be closed, the contacts Ill and I52 will be reengaged. The burner is then in condition tobe started up again on another demand for heat.

In the event that the high rate nozzle I0 fails to operate, when relay I48 drops out and shifts switch II3 back into engagement with the con tact I22, combustion ceases and the burner thermostat I5I starts to cool. The contacts 208. which disengaged to cause relay I49 to drop out, will reengage very soon as the thermostat I5I cools but, since the fingers 2I2 and 2I3 are out of contact, the circuit to relay I46 cannot now be reestablished. The heater I91 will continue to heat up and in35 seconds (assuming 5 seconds to be consumed in the starting run at the low firing rate) switch I99 will close and will be held closed lishes a. circuit to the solenoids 88 and 16 as fol-- lows" wire II6, terminal II1, wire II8, closed switchI I4, wire II9, terminal I20, wire I98, closed switch I96, wire I98, closed switch I82, wire I96, solenoids 63 and 16,'wire I21 and wire I28. The solenoids are thus energized and operate to connect the low firing rate nozzle 9 to operate. This nozzle, being operative, combustion occurs and the stack thermostat II opens the switches 203 and 205 and these disconnect the heaters I98 and I91. This occurs before the heater I61 has had time enough to open switch I61. Following the opening of switches 203 and 205, the contacts I18 engage and shunt out the heater I61 and fiinally the contacts HI and I52 separate. The burner is now in running condition and continues in operation until the demand for heat is satisfied and the burner is stopped by the opening of the room thermostat switch II5.

On a subsequent starting of the burner, with the high rate nozzle I0 inoperative and the switch I 96 locked in closed position, the burner will start up as before at the low firing rate and continue to operate at such rate. With switch II3 engaging contact I40, there will be a circuit through wire I39, terminal I38, wire I31, terminal I31, mercury I29, terminal I42, wire I94, switch I92, and wire I95 to the solenoids 63 and 16, as well as a circuit through wire I99, locked-in switch I96, wire I98, closed switch 192 and wire I95 to the solenoids. The movement of switch II3 to contact I22 will therefore not stop the energization of the solenoids and low firing rate operation will continue. If on any subsequent start the nozzle 9 fails to operate, then switch I92 will open in seconds and be locked out by latch 200. This will break the circuit to the solenoids, previously established by the locked in switch I96 and connect the nozzle I0 to the pump but, since this nozzle is also inoperative, no combustion will ocour and heater I61 will open switch I61 and the burner will stop in a manner such as to require manual resetting of switches I61, I92 and I96 before the burner can again be operated. While running on nozzle 9, if a failure of combustion occurs, contacts burner and after the one minutescavenging period, as previously described, the burner will attempt to start but will be locked out as described in the preceding sentence. 4

Assuming now, that, while the selector switch I I0 is set, as shown, for high firing rate operation, the high firing rate nozzle I0 is operative but the low firing rate nozzle 9 is inoperative when the burner starts, the solenoids 63 and 16 -will be energized through the circuit comprising wire II6,-terminal 1, wire II8, closed switch II4, wire II9, terminal I20, wire I, closed switch II3, contact I40, 'wire I39, terminal I38, wire I31, terminal I31, mercury I29, terminal I42,

wire I94, switch I92, wire I95, solenoids 63 and Since there is no 16, and wires I21 and I28. combustion contacts 208 remain closed leaving switch H3 in engagement with contact I22 and switch 203 remains closed. The heater I93 will be energized through a circuit which is the same as that just described up to and through the wire I94 and which then extends through heater I93, wire 202, switch 203, wires 206 and 201, terminal I90 and wires I9I, and I28. The heater I93 will cause switch I92 to open in 20 seconds to break the energizing circuit for the solenoids 63 and 16 and cause a shift from the low firing rate nozzle 9 to the high firing rate nozzle I0. The switch I92 looks out. The heater I81 for switch I96 I18 will open, stopping the i 18 started to heat up coincidentally with the heater I 83 through the following circuit: wire II6, terminal II1, wire II8, closed switch II4, wire II9, terminal I20, wire I99, heater I91, wire 204, closed switch 205, wire 201, terminal I90 and wires I9I and I28. This switch I96 if actuated, would close a circuit to the solenoids and prevent high firing rate operation, but the heater I91 requires 40 seconds to actuate switch I96 so that switch I92 will open well before switch I96 can close. Meanwhile, as combustion occurs from the nozzle I0, the stack thermostat I5I opens contacts 208 to disconnect relay I46, and shortly afterward, opens the switches 203 and 206 to demergize the heaters I93 and I91. This occurs before the contacts I18 engage. Operation of the burner at the high .rate will continue, when switch II3 moves into engagement with contact I22, following the dropping out of relay I46, because there will then be no closed circuit to the solenoids 63 and 16: the circuit through terminal I22, wire I 23, terminal I 24 and wire I25 being broken at the terminals III and H2. In theevent that the high rate nozzle I0 was inoperative when the switch I92 opened, as above described, the heater I91 will in 20 seconds more cause switch I96 to close and lock in closed position but since switch I92 has been locked in open position, the circuit to the solenoids will still be open. Since there is no combustion, the thermostat I5I cannot operate any of its contacts or switches and the heater I61 continues to heat up until in 50 seconds'more, it causes switch I61 to open and stop the burner.

In the case of the unsuccessful start of the low firing rate followed by successful operation at the high firing rate, following the opening of switch I92, and failure of the high rate nozzle I0 occurs during operation, then the burner will stop almost, immediately when the contacts I18 open, following the first slight drop in temperature after cessation ofcombustion. After the one minute scavenging period, the burner will start up again. When switch II3 engages the contact I40, the circuit, which it controls to the solenoids 63 and 16, will be broken by the open and locked: out switch I92; the heater I91 will in 40 seconds cause switch I96 to close but the circuit which it controls to-.the' solenoids is broken by the open switch I 92. The heater I61 in 50 seconds more will cause switch I61 to open and stop the burner in a manner such as to require manual resetting before further operation of the burner can occur.

Assuming next that the selector switch IIO is set for low firing rate operation, being tipped in.

' the opposite direction from that illustrated, and

that the high rate nozzle I0 is operative, when the room thermostat II5 calls for heat, the relays I46 and I41 will pull in simultaneously. The fingers 2I2 and H3 will remain in contact. The switches II4, I48, I49 and I50 will be closed by relay I41. The switch I I3 will be moved by relay I46 to engage contact I40. The energizing circuit for the solenoids 63 and 16, which circuit the switch I I3 controls, is broken at the terminals I31 and I42. Accordingly the solenoids remain deenergized and the high rate nozzle I0 is connected to operate and doesoperate. In say five seconds after combustion occurs, the thermostat I5I causes contacts 208 to separate and relay I46 to drop out and shift'switch 3 back to'contact I22. Meanwhile, relay I46 has moved finger 2I2 out of contact ,with finger 2I3. On engagement of switch II3 with contact I22, a circuit is made to the solenoids 63 and 16 as follows: 'wire I I8, terminal I I1, wire I I8, closed switch I I4, wire II9, terminal I20, wire I2I, switch II3, contact I22, wire I23, terminal I24, wire. I26, terminal II2, mercury I29, terminal III, wire I94, switch I92, wire I95, solenoids 69 and 10, and wires I21 and R8, The solenoids, being energized, the low rate nozzle 9 is connected for operation. If now, this nozzle 9 operates, combustion continues and the stack thermostat II will open switches 203 and 205 to disconnect the heaters I93 and I91 in time to prevent either time switch I92 or I96 from being actuated. Then, the contacts I13 will be engaged to shunt out the heater I61 and finally the contacts HI and IE2 will be separated and the burner will be in running condition. It will be noted that the heater I91 started warming up when switches I I4 and I I3 closed and that it will have been warming up for a period ofabout five v seconds before switch II3 moves to contact I22. Accordingly, the heater I91 cannot actuate its switch I96 for 35 seconds more and long before this, the switch 295 will have been opened by the stack thermostat to disconnect the heater I91.

In the event that the nozzle 9 fails to operate, I

when switch H3 is moved to engage contact I22, combustion ceases and the stack thermostat I9I commences to cool. The contacts 298, which separated to cause relay I99 to drop out and shift switch H3 back to contact I22 will reengage in-a short time but the fingers 2I2 and 2I3 are out of contact so that the relay I-IB cannot be actuated to move switch I I3 at this time. This gives time for the heater I93 to open switch I92 and break the circuit to the solenoids 93 and 13, deenergizing the latter and thereby causing the high rate nozzle III to be connected for operation. The switch I92 will 'be locked out. If this nozzle I0 operates, the burner thermostat I5I will separate the contacts 209, then open switches 203 and 295, then engage the contacts I13, then successively separate the pairs of contacts Ill and I52. The heater I91 will be shunted out and the burner placed in normal running condition, operating at the high iiring rate and continuing until the demand for heat is satisfied or a failure of combustion occurs, when the burner will be stopped in the same way as heretofore described.

On a subsequent start of the burner, the high ratenozzle ill will operate, as before, until the switch H3 is moved to contact I22 by the dropping out of relay I46, in response to the separation of contacts 208 in five seconds after occurrence of combustion. The circuit to the solenoids 63 and 16, which circuit would normally be made when switch I I3 engages contact I22, is broken by the locked out switch I92, wherefore combustion continues at the high rate. The thermostat I5I will operate, as before described, until the burner is in normal running condition. Combustion continues until the demand for heat is satisfied or combustion fails, when the burner will stop in the manner heretofore described.

In the-event that the low rate nozzle 9 operates successfully for a time after switch H3 is' moved back to engage contact I22, following a successful five seconds run at the high firing rate, and then fails before the demand for heat is satisfied, the contacts I18 will separate, immediately stopping the burner. After the one minute scavenging period, the burner will recycle and operate at the high rate for five seconds, when the contacts 208 will be separated by the stack thermostat I5I to cause switch H3 to move back to contact I22. Combustion ceases because the low rate nozzle is inoperative and the stack thermostat cools. Since burner. However, the heater I93 .will in 20 seconds open switch I92, which is locked out by latch 200, breaking the circuit to the solenoids and connecting the nozzle I0 to operate and high firing rate operation will occur in'time to preventthe clolsing of switch I96 and the opening of switch I9 Assuming now that the high rate nozzle I0 is inoperative, when the burner is started up by the closure of room thermostat I I5, the relays I46 and I91 pull in as before, closing the switches which they control. Combustion does not occur and the nozzle I0 is connected to operate but the contacts 298 remain engaged. The circuit to the solenoids, then controlled by switch H3, is open at the terminals I31 and I92 of the selector switch. The heater I93 is therefore out of circuit. However, the heater I91 is connected in the following circuit: wire H3, terminal 1, wire II8, closed switch H9, wire H9, terminal I20, wire I99, heater I91, wire 209, closed switch 205, wire 201, terminal I90, and wires WI and I23. In 40 seconds, the switch I99 will close and become locked in closed position. This establishes a circuit to solenoids 63 and 16 as follows: wire H9, terminal H1, wire H8, closed switch II4, wire II9, terminal I29, wire I99, closed switch I96, wire I98, closed switch I92, wire I95, solenoids 93 and 19, and wires I21 and I28. The solenoids, being energized, the low rate nozzle is connected to operate. Combustion occurs, and the contacts 209 separate causing M3 to move to contact I22 and this establishes a parallel circuit to wire I99. The closing of switch I99, also closes a circuit to the heater I 93, which is the same as that described up through the wire I98 and then extends as follows: heater I93, wire 202, closed switch 203, wires 209 and 201, terminal I99, and wires I9I and I23. This heater I93 requires 20 seconds to open its switch I92 and in about 10 seconds after combustionoccurs, the switches 293 and 235 will be opened by the stack thermostat I5I to disconnect the heater I93. The stack thermostat then actuates thecontacts I18, I1! and I52, as before described, to put the burner in normal running condition.

If the low rate nozzle 9 fails, the heater I93 will in 20 seconds open the switch I92, which becomes locked out. The circuit to the solenoids 93 and 16, is broken and the nozzle I0 is connected to operate but, since it is not operative, the failure of combustion continues and in seconds after the closing of switch II4, the heater I61 will open switch I61 and stop the burner. The

switches I31, I92 and I96 will have to be manually switch II3, the auxiliary selector switch I31, I42

and its connections to switch II3, the contacts 203 and contact fingers 2I2 and U3. The relay I41 is connected to the left side of the secondary, I65 by a wire 233 instead of through the twogwires 209 and 2! as formerly and a supply wire 234 connects the terminal II2 of selector switch H0 to the wire I99. Otherwise, the parts are the same as shown in Fig. 14 and function in the same way.

The operation of the control system shown in Fig. 1'1 will next be described. On a demand for heat from the burner, the room thermostat II6 closes a circuit to the relay I41 as follows: from the right hand terminal of secondary I66, wire 2I0, terminal I59, wire I51, contact I54, blade-I69, contact I56, wire I58, terminal I90, wires H1 and 224, engaged pairs of contacts "I and I62, wire 22I, heater I61, wire,220, closed switch I61, wire '2I9, relay coil I41, and wire 233 back-to the left hand side of secondary I65. The relay I41 pulls in, closing switch I-I4, which startsthe motor 9 and energizes the ignition transformer, and also closing switches I46, I49 and'I50. The switch II4 also controls the primary energizing circuit for the solenoids 63 and 16, which circuit includes wire II6, terminal II1, wire II8, switch II4, wire II9, terminal I20, wire I99 as far as wire 234, wire 234, terminals H2 and III of switch IIO, wire I94, time switch. I92, wire I95, solenoids 63 and 16 and wires I21 and I28. This energizing circuit is now open at the terminals III and H2 so that the solenoids will not be energized and the high rate nozzle I will be connected to operate.

The heater I91 of time switch I96 is energized, when switch I I4 closes, through the followingv circuit: wire II6, terminal II1, wire II6, switch II4, wire II9, terminal I20, wire I99, heater l91, wire 204, switch 205, wire 201, terminal I90 and wires IN and I 28. If the nozzle I0 operates, combustion occurs and the stack thermostat I 5I .will open switch 205, in say seconds, and disconnect the heater I91 and thus prevent switch I96 from closing. Also,'the thermostat I5I will, as before, cause contacts I18 to engage and then cause the pairs of contacts HI and I52 to successively separate. The heater I61 will be shunted out,

when contacts I18 engage, and the burner placed in normal running condition as before.

the nozzle I 0 fall during a normal run of the burner instead of at the starting of the burner, then contacts I19 will be separated by thermostat I6I soon after combustion failure. The burner will stop and, after the one minute scavenging period, it will automatically start up again and then the heater I91 will be energized and in 40 seconds close switch I96, as before described to render the low rate nozzle 9 operative.

'be shunted out to prevent the opening of switch I61. If nozzle 9 fails to operate, the switches 209 and 206 will not be opened by the'stack thermostat Ill and in 20 seconds the heater I93 will cause switch I92 to open and break the pri- I mary energizing circuit to the solenoids, causing the nozzle II to be connected to operate. Switch I92 is locked out by latch 200. If nozzle I0 operates, the thermostat III will open switch 206 to disconnect heater I91 and prevent it from closing switch I99. Also, heater I61 will be shunted out as before described. If nozzle I0 fails to operate, the heater I91 will in 20 seconds more cause switch I96 to close but this is ineffective since the switch I92 is open and the energizing circuit to the solenoids is broken. In 30 If, when the switch I I4 was closed to start the burner, the nozzle I0 failed to operate, there would be no combustion and the stack thermostat I5I would not open switch 205. Accordingly, the heater I91 would continue to be energized and it would in a predetermined time, say 40 seconds,

cause switch I96 to close and become locked in by the latch 20I. An alternate energizing circuit to the solenoids would then be closed as follows: wire-I I6, terminal II1, wire II8, closed switch II4,

Wire II9, terminal I20, wire I99, closed switch I96, wire I98, closed switch I92, wire I95, solenoids 63 and 16, and wires' I21, and I28. The solenoids will be energized and cause nozzle 9 to be connected to operate. When the switch I I 4 is closed, it closes a circuit to the heater I93 which is the same as the last-named circuit up through the wire I98 and thence extends by heater I93, wire 202, closed switch 203, wires 206 and 201, terminal I99 and wires I 9| and I28. If the nozzle 9 operates, the stack thermostat will function as before and open switch 203 before heater I93 can open switch I92 and the burner will operate at the low rate in the emergency. If the nozzle 9 does not operate, the heater I93 will in 20 seconds more cause switch I92 to open and become locked out by latch 200, opening the circuit to the solemold and causing the nozzle I0 to be connected to operate. Since the nozzle I0 is inoperative,

combustion does not occur and in 30 seconds more 1 seconds more, heater I91 will cause switch I61 to open and stop the burner. Manual resetting of switches I91, I92, and I96 will then be rcquired.

Should the nozzle 9 fall during a normal run of the burner, the contacts I18 will be opened, shortly after cessation of combustion, to stop the burner. Then, after the one minute scavenging period, the burner will start up again and in 20 seconds the heater I93 will open switch I92,

as before described, to cause the nozzle I0 to be connected to operate.

In the control systems described, the parts within the dot-dash rectangle 206 in Fig. .13 constitute one control instrument. That is, the two relays and the several switches operated by them-the transformer I66, the safety switch I61 and the several switches operated by the stack thermostat I6I are all contained within a single small casing, which may be mounted on the stack of the heating apparatus with the sensitive element of the stack thermostat I5I extending into the stack. The room thermostat H6 will be located in the desired room-of the house to be heated and wired up to the aforesaid control instrument in the usual way. The selector switch I III will be located adjacent its actuating thermostat -I30 and wired up to said control instrument and to the solenoids 63 and 16 on the burner. The burner motor and ignition transformer are wired up in the usual manner to said control instrument. The ignition transformer may be located within a casing 209', suitably secured to the casting 6, as indicated in Figs. 3 and 5, with the insulators 2I0 carrying the high tension terminals 2II', projecting partly into the air conduit 1, as shown in Fig. 5, to receive the wires Assume now that the selector switch IIO'is set 

